JP2003319631A - Brushless motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a brushless motor which can be reduced in size by omitting an axial space for arranging a position sensor for the detection of a rotor position. <P>SOLUTION: In this brushless motor M which is equipped with a rotor 30 having a rotary shaft 22, a rotor core 24 where the rotary shaft is inserted, and a magnet 26 arranged around the rotor core 24, a stator 30 which is provided around the rotor 20, and a position sensor 52 which detects the rotational position of the rotor 20 by a magnetic change, the rotor 20 has a sensor space 24a formed between the rotary shaft 22 and the inside periphery of the magnet 26, and the position sensor 52 is arranged in the sensor space 24a. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor, and more particularly to a brushless motor that detects a rotational position of a rotor by using a position sensor such as a Hall element.

[0002]

2. Description of the Related Art A brushless motor is provided with a stator composed of a plurality of iron cores having windings, and a rotating magnetic field is generated when a current is sequentially applied to the windings. The brushless motor is configured such that the rotor rotates due to the interaction between the rotating magnetic field and the magnetic field generated by the magnet or the windings arranged on the rotor.

The brushless motor includes a control board having a position sensor and a control unit for detecting the rotational position of the rotor, and based on the signal of the current rotational position of the rotor detected by the position sensor. The control unit controls the power supply to the predetermined winding at an appropriate timing. As the position sensor, for example, a Hall element, a Hall IC, an encoder, a resolver or the like is used.

FIG. 5 is a sectional view of a conventional inner rotor type brushless motor M. Brushless motor M
Is a rotor 20 having a rotary shaft 22 inserted therein,
Bearings 41, 42 for rotatably supporting the stator, a stator 30 having a winding 32 wound around an iron core 31, a control board 50,
A yoke housing 40 and an end plate 44 that accommodate these are provided.

The rotor 20 has a structure in which a rotating shaft 22 is inserted into an inner through hole of a cylindrical rotor core 24, and a magnet 26 is arranged on the outer peripheral surface of the rotor core 24. The control board 50 includes a position sensor 52 composed of a Hall element, a control IC (not shown), and the like on the board.
Controls the operation of the brushless motor M based on the position detection signal from the position sensor 52.

Since the distance between the magnet 26 and the stator 30 is normally set to be as close as possible in order to improve the magnetic efficiency, the position sensor 52 is not arranged between the magnet 26 and the stator 30. It has become difficult.

For this reason, the magnet 26 is attached to the stator 3
0 is extended to the left side in the axial direction in the drawing. The position sensor 52 is arranged so as to be located radially outside the extending portion of the magnet 26. With such a configuration, the position sensor 52 can detect the magnetism in the radial direction from the extending portion of the magnet 26 when the rotor 20 rotates.

FIG. 6 is a sectional view of another conventional brushless motor M. In the brushless motor M of FIG. 6, the sensor magnet 26a is arranged on one end surface of the magnet 26 (or the rotor core 24) in the axial direction. The position sensor 52 is the sensor magnet 2
The magnetism in the axial direction from 6a can be detected.

[0009]

In the brushless motor M according to FIG. 5, in order to detect the position of the rotor 20, the magnet 26 is extended in the axial direction, and the position sensor 52 is arranged so as to face the extended portion. It has been configured. Therefore, there is a problem that the axial length of the brushless motor M becomes large. Since this extended portion does not face the stator 30, it does not substantially contribute to the generation of the rotational driving force of the brushless motor M. That is, there is a problem that the size of the brushless motor M becomes larger than the obtained rotational driving force.

In the brushless motor M according to FIG. 6, the sensor magnet 26a is arranged on one end surface of the magnet 26 (or the rotor core 24) in the axial direction. Therefore, it is not necessary to extend the magnet 26 in the axial direction, and the magnet 26 can perform position detection without increasing the size of the brushless motor M as compared with the conventional example shown in FIG. Further, since it is possible to face the stator 30 over substantially the entire axial length thereof, the portion that does not substantially contribute to the generation of the rotational driving force of the brushless motor M is reduced.

However, even in this case, a space for arranging the position sensor 52 and the sensor magnet 26a is required between the control board 50 and one end surface of the magnet 26 (or the rotor core 24). Therefore, there is a problem that the axial length of the brushless motor M is increased by the space.

In view of the above problems, an object of the present invention is to provide a brushless motor which can be downsized by eliminating the axial space portion for disposing the position sensor for detecting the rotor position.

[0013]

According to the brushless motor of claim 1, a rotor having a rotating shaft, a rotor core to which the rotating shaft is attached, and a magnet provided integrally with the rotor core are provided. And a stator provided on the outer periphery of the rotor, and a position sensor for detecting a rotational position of the rotor by magnetic change, wherein the rotor includes the rotating shaft and the magnet. The position sensor has a space formed between itself and the peripheral surface, and the position sensor is solved by being arranged in the space.

As described above, since the position sensor is arranged in the space inside the end of the magnet in the axial direction, the axial length of the stator is set to the rotor in order to arrange the position sensor in the axial direction as in the conventional case. Since it is not necessary to make the brushless motor relatively shorter than the axial length of the magnet or to extend the axial length of the brushless motor, the brushless motor can be downsized.

Further, as described in claim 2, a sensor magnet for detecting the position of the position sensor may be arranged at the end of the rotor core in the space. This is preferable because the position sensor can detect a magnetic change in the axial direction or the radial direction.

Further, according to the brushless motor of the present invention, the above object is to provide a rotor having a rotating shaft, a rotor core having the rotating shaft inserted therein, and a magnet arranged on an outer peripheral surface of the rotor core. A brushless motor comprising: a stator provided on the outer circumference of a rotor; and a position sensor that detects a rotational position of the rotor by a magnetic change, wherein the rotor core opens in an axial end surface of the rotor core and is axially extended. It has a recess formed and the position sensor is solved by being arranged in the recess.

As described above, since the position sensor is arranged in the recess formed at the end of the rotor core, there is no need to secure a space for arranging the position sensor in the axial direction as in the conventional case, and the brushless The motor can be downsized.

Further, as described in claim 4, a sensor magnet for detecting the position of the position sensor may be arranged in the recess. This is preferable because it is possible to change the relative positional relationship between the position sensor and the sensor magnet by disposing the sensor magnet according to the shape of the recess.

Further, according to a fifth aspect of the present invention, the stator is provided with an insulator, and a sensor holder that extends inward in the radial direction is provided at an end portion of the insulator in the rotation axis direction. Is preferable because it can be easily positioned in the circumferential direction of the position sensor by being arranged on the sensor holder.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings. Further, the arrangement, shape, etc. described below are not intended to limit the present invention, and it goes without saying that various modifications can be made in accordance with the spirit of the present invention.
The same components as those of the brushless motor according to the conventional example are designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1 is a vertical sectional view of a brushless motor of the embodiment, FIG. 2 is a sectional view of a brushless motor of the embodiment, and FIGS. 3 and 4 are explanatory views of a position sensor of a brushless motor of another embodiment.

As shown in FIGS. 1 and 2, the brushless motor M includes a rotor 20, a stator 30, and a control board 50.
And a yoke housing 40 and an end plate 44 that accommodate them.

In the rotor 20, the rotating shaft 22 is inserted into a rotor core 24 having a through hole, magnets 26 are arranged on the outer peripheral surface of the rotor core 24 so that the polarities alternate in the circumferential direction, and the magnets 26 are further covered. The rotor cover 28 is attached to the.

The axial length of the rotor core 24 is shorter than the axial lengths of the magnet 26 and the rotor cover 28, and the output side of the rotor core 24 is an annular recess surrounded by the inner peripheral surface of the magnet 26. Sensor space 24a
Are formed.

The stator 30 has a structure in which the iron core 31 around which the winding 32 is wound is inserted and attached to the insulator 34, and the plurality of insulators 34 are arranged so as to contact the inner surface of the yoke housing 40. There is. Further, the ends of the winding 32 are electrically joined so as to form a Y connection,
The three-phase (U-phase, V-phase, W-phase) windings are arranged as shown in FIG.

The stator 30 of the brushless motor M of this embodiment has a structure in which the winding 32 is wound around each of a plurality of iron cores 31, but the present invention is not limited to this, and a laminated stator core having a plurality of teeth. The stator 30 may be configured such that an insulator is attached to an iron core made of and the winding 32 is wound around the insulator.

The control board 50 is a printed board having an opening at the center for inserting the rotary shaft 22 therethrough. A control IC and other electric parts are arranged on the control board 50, and a plurality of position sensors 52 each composed of a Hall element (Hall IC) are arranged. Then, the control board 50
Are positioned and arranged so as to abut the inner surface of the yoke housing 40.

The position sensor 52 has a sensor space 24a.
It is arranged so as to face the inner peripheral surface of the magnet 26 of the rotor 20 facing inside. With this configuration, it is not necessary to provide a space for disposing the position sensor 52 between the magnet 26 and the control board 50 as in the conventional case, and the axial length of the brushless motor M can be shortened. Becomes

The yoke housing 40 has a cylindrical shape with a bottom, and a bearing mounting portion 42a is bulged at the bottom. Further, the end plate 44 is also formed with a bearing mounting portion 41a. Bearings 41 and 42 are press-fitted and fixed in the bearing mounting portions 41a and 42a, respectively, and the bearings 41 and 42 rotatably support the rotor 20.

As described above, the brushless motor M of this example
Then, the rotor core 2 in which the magnet 26 is arranged on the outer peripheral surface
The axial length of 4 is set to be shorter than the axial length of the magnet 26, whereby a sensor space 24a in which the position sensor 52 can be arranged inside the magnet 26 in the radial direction is formed at one end of the magnet 26. To be done.
The position sensor 5 is placed in the sensor space 24a.
2 is arranged.

Conventionally, the magnet 26 is extended in the axial direction, or the sensor magnet 26a is provided on the end surface of the magnet 26 in the axial direction to secure a space for disposing the position sensor 52 in the axial direction of the brushless motor M. However, in the brushless motor M of this example, since the arrangement space of the position sensor 52 does not need to be provided in the axial direction of the brushless motor M in the configuration described above, the axial length of the brushless motor M can be shortened. Therefore, the size can be reduced.

Further, since the rotor core 24 is set to be short, the axial length of the magnet 26 can be secured, and the axial length of the magnet 26 and the axial length of the stator 30 can be made approximately the same. Therefore, the rotational drive force does not decrease as compared with the conventional one, and the same rotational drive force can be obtained.

The embodiment of the present invention may be modified as follows. In the above-described embodiment, the position sensor 52 is directly attached to the control board 50, but as shown in FIG. 3, the sensor holder 34a is provided integrally or separately at the end of the insulator 34 on the control board 50 side. The position sensor 52 may be arranged on the sensor holder 34a. Then, the position sensor 52 and the control board 50 are electrically connected.

With this structure, the insulator 3
Since it is possible to extend the sensor holding body 34a radially inward from a predetermined position end portion in the circumferential direction of 4, the position sensor 5
The circumferential mounting position of 2 can be easily positioned, and more stable holding can be achieved. Even when the stator 30 having a structure in which an insulator is attached to an iron core made of a laminated stator core having a plurality of teeth and windings are wound around the teeth is used, the sensor holder 34a is extended to the insulator. It's good to let them out.

In the above embodiment, the position sensor 52 detects the magnetism in the radial direction from the rotor 20 side. However, the present invention is not limited to this. The position sensor 52 detects magnetism in the axial direction. It may be configured to do so. In such a configuration, the sensor magnet 26a may be arranged on the axial end surface of the rotor core 24, and the position sensor 52 may be opposed to the sensor magnet 26a.

Further, in the above embodiment, the rotor core 24
Since the axial length of the magnet 26 is shorter than the axial length of the magnet 26, the inner peripheral surface of the magnet 26 is exposed to the sensor space 24a at one end side, and the position sensor 52 is connected to the exposed inner peripheral surface of the magnet 26. It is configured to be able to face each other.

However, as shown in FIG.
If a recess for mounting the sensor for forming the sensor space 24a is formed on one end side, the inner surface of the magnet 26 is covered by the wall 24b. Therefore, the sensor magnet 26a may be separately provided on the wall portion 24b so that the position sensor 52 can reliably detect the rotational position of the rotor 20.

In this case, the sensor mounting recess for forming the sensor space 24a need not be a cylindrical surface as shown in FIG. 4, and may be, for example, a polygonal surface, an axial stepped surface, an inclined curved surface, It may be an inclined plane or the like.

When the sensor space 24a is formed as a recess as described above, the wall portion covering the rotary shaft 22 is separated from the rotor core 24 in the same manner as the inner peripheral surface of the magnet 26 is covered by the wall portion 24b. It may be extended. In this case, the magnet 2 is attached to the wall side that covers the rotary shaft 22.
6 may be provided. In addition, when the wall portion that covers the rotating shaft 22 is extended from the rotor core 24,
The wall portion 24b that covers the inner peripheral surface of the magnet 26 may not be formed.

Further, the wall portion 24b of the sensor space 24a
Alternatively, a recess for attaching the sensor magnet 26a is provided on the end face or the like, and the sensor magnet 26a is provided in the recess.
You may arrange so that it may fit.

The technical ideas other than the claims that can be understood from the above embodiment will be described below. (1) In the motor according to any one of claims 1 to 4, the stator includes a stator core having a plurality of teeth and an insulator that covers the teeth of the stator core, and an end portion of the insulator in the rotation axis direction. The brushless motor is characterized in that a sensor holder extending radially inward is provided, and the position sensor is arranged on the sensor holder. With such a configuration, the position sensor can be easily positioned in the circumferential direction, and the position sensor can be reliably held.

[0042]

As described above, according to the brushless motor of the present invention, it is not necessary to provide a space in the axial direction of the brushless motor in order to dispose the position sensor for detecting the rotor position. Thus, it is possible to provide a brushless motor that has the same rotational driving force and has a reduced axial length to be downsized.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a brushless motor according to an embodiment.

FIG. 2 is a cross-sectional view of a brushless motor according to an embodiment.

FIG. 3 is an explanatory diagram of a position sensor of a brushless motor according to another embodiment.

FIG. 4 is an explanatory diagram of a position sensor of a brushless motor according to another embodiment.

FIG. 5 is a vertical sectional view of a conventional brushless motor.

FIG. 6 is a vertical sectional view of a conventional brushless motor.

[Explanation of symbols]

20 rotor, 22 rotating shaft, 24 rotor core, 24
a sensor space, 24b wall portion, 26 magnet, 26a sensor magnet, 28 rotor cover, 30 stator, 31 iron core, 32 winding wire, 34
Insulator, 34a sensor holder, 40 yoke housing, 41, 42 bearing, 41a, 42a bearing mounting portion, 44 end plate, 50 control board, 52
Position sensor, M brushless motor

Claims (5)

[Claims] 1. A rotor having a rotating shaft, a rotor core into which the rotating shaft is inserted, a magnet provided integrally with the rotor core, and a stator provided on the outer periphery of the rotor.
A brushless motor comprising: a position sensor that detects a rotational position of the rotor by a magnetic change, wherein the rotor has a space formed between the rotating shaft and an inner peripheral surface of the magnet. The brushless motor, wherein the position sensor is arranged in the space. 2. The brushless motor according to claim 1, wherein a sensor magnet for detecting the position of the position sensor is arranged at an end of the rotor core in the space. 3. A rotor having a rotating shaft, a rotor core having the rotating shaft inserted therein, a magnet arranged on an outer peripheral surface of the rotor core, a stator provided on the outer periphery of the rotor, and a rotating position of the rotor. A position sensor that detects by magnetic change, and a rotor core, the rotor core has a recessed portion that is formed in the axial direction while opening in the axial end surface of the rotor core, the position sensor, in the recessed portion Brushless motor characterized by being arranged. 4. The brushless motor according to claim 3, wherein a sensor magnet for detecting the position of the position sensor is provided in the recess. 5. The stator includes an insulator, a sensor holding body extending inward in a radial direction is provided at an end portion of the insulator in a rotation axis direction, and the position sensor is disposed on the sensor holding body. The brushless motor according to claim 1, wherein the brushless motor is provided.